package com.propn.golf.tools;

/**
 * 
 * @author <a href="mailto:zhangyouqun@gmail.com">cnoss (QQ:86895156)</a>
 * 
 */
public final class MD5Util {
    /** DOCUMENT ME! */
    private static final int S11 = 7;

    /** DOCUMENT ME! */
    private static final int S12 = 12;

    /** DOCUMENT ME! */
    private static final int S13 = 17;

    /** DOCUMENT ME! */
    private static final int S14 = 22;

    /** DOCUMENT ME! */
    private static final int S21 = 5;

    /** DOCUMENT ME! */
    private static final int S22 = 9;

    /** DOCUMENT ME! */
    private static final int S23 = 14;

    /** DOCUMENT ME! */
    private static final int S24 = 20;

    /** DOCUMENT ME! */
    private static final int S31 = 4;

    /** DOCUMENT ME! */
    private static final int S32 = 11;

    /** DOCUMENT ME! */
    private static final int S33 = 16;

    /** DOCUMENT ME! */
    private static final int S34 = 23;

    /** DOCUMENT ME! */
    private static final int S41 = 6;

    /** DOCUMENT ME! */
    private static final int S42 = 10;

    /** DOCUMENT ME! */
    private static final int S43 = 15;

    /** DOCUMENT ME! */
    private static final int S44 = 21;

    /** DOCUMENT ME! */
    private static final byte[] PADDING = { -128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0 };

    // ~ Instance fields
    // ========================================================

    /*
     * digestHexStr是MD5的唯一一个公共成员，是最新一次计算结果的 16进制ASCII表示.
     */

    /** DOCUMENT ME! */
    private String digestHexStr;

    // number of bits, modulo 2^64 (lsb first)

    /** DOCUMENT ME! */
    private byte[] buffer = new byte[64]; // input buffer

    /** DOCUMENT ME! */
    private long[] count = new long[2];

    /*
     * digest,是最新一次计算结果的2进制内部表示，表示128bit的MD5值.
     */

    /** DOCUMENT ME! */
    private byte[] digest = new byte[16];

    /*
     * 下面的三个成员是MD5计算过程中用到的3个核心数据，在原始的C实现中 被定义到MD5_CTX结构中
     */

    /** DOCUMENT ME! */
    private long[] state = new long[4]; // state (ABCD)

    // ~ Constructors
    // ===========================================================

    // 这是MD5这个类的标准构造函数，JavaBean要求有一个public的并且没有参数的构造函数
    public MD5Util() {

        md5Init();

        return;
    }

    // ~ Methods
    // ================================================================

    /**
     * DOCUMENT ME!
     * 
     * @param source DOCUMENT ME!
     * 
     * @return DOCUMENT ME!
     */
    public static String toMD5(String source) {

        MD5Util md5 = new MD5Util();

        return md5.getMD5ofStr(source);
    }

    /*
     * getMD5ofStr是类MD5最主要的公共方法，入口参数是你想要进行MD5变换的字符串 返回的是变换完的结果，这个结果是从公共成员digestHexStr取得的．
     */
    private String getMD5ofStr(String inbuf) {

        md5Init();
        md5Update(inbuf.getBytes(), inbuf.length());
        md5Final();
        digestHexStr = "";

        for (int i = 0; i < 16; i++) {

            digestHexStr += byteHEX(digest[i]);
        }

        return digestHexStr;
    }

    /*
     * Decode把byte数组按顺序合成成long数组，因为java的long类型是64bit的， 只合成低32bit，高32bit清零，以适应原始C实现的用途
     */
    private void Decode(long[] output, byte[] input, int len) {

        int i;
        int j;

        for (i = 0, j = 0; j < len; i++, j += 4) {

            output[i] = b2iu(input[j]) | (b2iu(input[j + 1]) << 8) | (b2iu(input[j + 2]) << 16)
                    | (b2iu(input[j + 3]) << 24);
        }

        return;
    }

    /*
     * Encode把long数组按顺序拆成byte数组，因为java的long类型是64bit的， 只拆低32bit，以适应原始C实现的用途
     */
    private void Encode(byte[] output, long[] input, int len) {

        int i;
        int j;

        for (i = 0, j = 0; j < len; i++, j += 4) {

            output[j] = (byte) (input[i] & 0xffL);
            output[j + 1] = (byte) ((input[i] >>> 8) & 0xffL);
            output[j + 2] = (byte) ((input[i] >>> 16) & 0xffL);
            output[j + 3] = (byte) ((input[i] >>> 24) & 0xffL);
        }
    }

    /*
     * F, G, H ,I 是4个基本的MD5函数，在原始的MD5的C实现中，由于它们是 简单的位运算，可能出于效率的考虑把它们实现成了宏，在java中，我们把它们 实现成了private方法，名字保持了原来C中的。
     */
    private long F(long x, long y, long z) {

        return (x & y) | ((~x) & z);
    }

    /*
     * FF,GG,HH和II将调用F,G,H,I进行近一步变换 FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4. Rotation is separate
     * from addition to prevent recomputation.
     */
    private long FF(long a, long b, long c, long d, long x, long s, long ac) {

        a += (F(b, c, d) + x + ac);
        a = ((int) a << s) | ((int) a >>> (32 - s));
        a += b;

        return a;
    }

    /**
     * DOCUMENT ME!
     * 
     * @param x DOCUMENT ME!
     * @param y DOCUMENT ME!
     * @param z DOCUMENT ME!
     * 
     * @return DOCUMENT ME!
     */
    private long G(long x, long y, long z) {

        return (x & z) | (y & (~z));
    }

    /**
     * DOCUMENT ME!
     * 
     * @param a DOCUMENT ME!
     * @param b DOCUMENT ME!
     * @param c DOCUMENT ME!
     * @param d DOCUMENT ME!
     * @param x DOCUMENT ME!
     * @param s DOCUMENT ME!
     * @param ac DOCUMENT ME!
     * 
     * @return DOCUMENT ME!
     */
    private long GG(long a, long b, long c, long d, long x, long s, long ac) {

        a += (G(b, c, d) + x + ac);
        a = ((int) a << s) | ((int) a >>> (32 - s));
        a += b;

        return a;
    }

    /**
     * DOCUMENT ME!
     * 
     * @param x DOCUMENT ME!
     * @param y DOCUMENT ME!
     * @param z DOCUMENT ME!
     * 
     * @return DOCUMENT ME!
     */
    private long H(long x, long y, long z) {

        return x ^ y ^ z;
    }

    /**
     * DOCUMENT ME!
     * 
     * @param a DOCUMENT ME!
     * @param b DOCUMENT ME!
     * @param c DOCUMENT ME!
     * @param d DOCUMENT ME!
     * @param x DOCUMENT ME!
     * @param s DOCUMENT ME!
     * @param ac DOCUMENT ME!
     * 
     * @return DOCUMENT ME!
     */
    private long HH(long a, long b, long c, long d, long x, long s, long ac) {

        a += (H(b, c, d) + x + ac);
        a = ((int) a << s) | ((int) a >>> (32 - s));
        a += b;

        return a;
    }

    /**
     * DOCUMENT ME!
     * 
     * @param x DOCUMENT ME!
     * @param y DOCUMENT ME!
     * @param z DOCUMENT ME!
     * 
     * @return DOCUMENT ME!
     */
    private long I(long x, long y, long z) {

        return y ^ (x | (~z));
    }

    /**
     * DOCUMENT ME!
     * 
     * @param a DOCUMENT ME!
     * @param b DOCUMENT ME!
     * @param c DOCUMENT ME!
     * @param d DOCUMENT ME!
     * @param x DOCUMENT ME!
     * @param s DOCUMENT ME!
     * @param ac DOCUMENT ME!
     * 
     * @return DOCUMENT ME!
     */
    private long II(long a, long b, long c, long d, long x, long s, long ac) {

        a += (I(b, c, d) + x + ac);
        a = ((int) a << s) | ((int) a >>> (32 - s));
        a += b;

        return a;
    }

    /*
     * b2iu是我写的一个把byte按照不考虑正负号的原则的＂升位＂程序，因为java没有unsigned运算
     */
    private static long b2iu(byte b) {

        return (b < 0) ? (b & (0x7F + 128)) : b;
    }

    /*
     * byteHEX()，用来把一个byte类型的数转换成十六进制的ASCII表示， 因为java中的byte的toString无法实现这一点，我们又没有C语言中的 sprintf(outbuf,"%02X",ib)
     */
    private static String byteHEX(byte ib) {

        char[] Digit = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
        char[] ob = new char[2];
        ob[0] = Digit[(ib >>> 4) & 0X0F];
        ob[1] = Digit[ib & 0X0F];

        String s = new String(ob);

        return s;
    }

    /*
     * md5Final整理和填写输出结果
     */
    private void md5Final() {

        byte[] bits = new byte[8];
        int index;
        int padLen;

        // /* Save number of bits */
        Encode(bits, count, 8);

        // /* Pad out to 56 mod 64.
        index = (int) (count[0] >>> 3) & 0x3f;
        padLen = (index < 56) ? (56 - index) : (120 - index);
        md5Update(PADDING, padLen);

        // /* Append length (before padding) */
        md5Update(bits, 8);

        // /* Store state in digest */
        Encode(digest, state, 16);
    }

    /* md5Init是一个初始化函数，初始化核心变量，装入标准的幻数 */
    private void md5Init() {

        count[0] = 0L;
        count[1] = 0L;

        // /* Load magic initialization constants.
        state[0] = 0x67452301L;
        state[1] = 0xefcdab89L;
        state[2] = 0x98badcfeL;
        state[3] = 0x10325476L;

        return;
    }

    /*
     * md5Memcpy是一个内部使用的byte数组的块拷贝函数，从input的inpos开始把len长度的 字节拷贝到output的outpos位置开始
     */
    private void md5Memcpy(byte[] output, byte[] input, int outpos, int inpos, int len) {

        int i;

        for (i = 0; i < len; i++) {

            output[outpos + i] = input[inpos + i];
        }
    }

    /*
     * md5Transform是MD5核心变换程序，有md5Update调用，block是分块的原始字节
     */
    private void md5Transform(byte[] block) {

        long a = state[0];
        long b = state[1];
        long c = state[2];
        long d = state[3];
        long[] x = new long[16];

        Decode(x, block, 64);

        /* Round 1 */
        a = FF(a, b, c, d, x[0], S11, 0xd76aa478L); /* 1 */
        d = FF(d, a, b, c, x[1], S12, 0xe8c7b756L); /* 2 */
        c = FF(c, d, a, b, x[2], S13, 0x242070dbL); /* 3 */
        b = FF(b, c, d, a, x[3], S14, 0xc1bdceeeL); /* 4 */
        a = FF(a, b, c, d, x[4], S11, 0xf57c0fafL); /* 5 */
        d = FF(d, a, b, c, x[5], S12, 0x4787c62aL); /* 6 */
        c = FF(c, d, a, b, x[6], S13, 0xa8304613L); /* 7 */
        b = FF(b, c, d, a, x[7], S14, 0xfd469501L); /* 8 */
        a = FF(a, b, c, d, x[8], S11, 0x698098d8L); /* 9 */
        d = FF(d, a, b, c, x[9], S12, 0x8b44f7afL); /* 10 */
        c = FF(c, d, a, b, x[10], S13, 0xffff5bb1L); /* 11 */
        b = FF(b, c, d, a, x[11], S14, 0x895cd7beL); /* 12 */
        a = FF(a, b, c, d, x[12], S11, 0x6b901122L); /* 13 */
        d = FF(d, a, b, c, x[13], S12, 0xfd987193L); /* 14 */
        c = FF(c, d, a, b, x[14], S13, 0xa679438eL); /* 15 */
        b = FF(b, c, d, a, x[15], S14, 0x49b40821L); /* 16 */

        /* Round 2 */
        a = GG(a, b, c, d, x[1], S21, 0xf61e2562L); /* 17 */
        d = GG(d, a, b, c, x[6], S22, 0xc040b340L); /* 18 */
        c = GG(c, d, a, b, x[11], S23, 0x265e5a51L); /* 19 */
        b = GG(b, c, d, a, x[0], S24, 0xe9b6c7aaL); /* 20 */
        a = GG(a, b, c, d, x[5], S21, 0xd62f105dL); /* 21 */
        d = GG(d, a, b, c, x[10], S22, 0x2441453L); /* 22 */
        c = GG(c, d, a, b, x[15], S23, 0xd8a1e681L); /* 23 */
        b = GG(b, c, d, a, x[4], S24, 0xe7d3fbc8L); /* 24 */
        a = GG(a, b, c, d, x[9], S21, 0x21e1cde6L); /* 25 */
        d = GG(d, a, b, c, x[14], S22, 0xc33707d6L); /* 26 */
        c = GG(c, d, a, b, x[3], S23, 0xf4d50d87L); /* 27 */
        b = GG(b, c, d, a, x[8], S24, 0x455a14edL); /* 28 */
        a = GG(a, b, c, d, x[13], S21, 0xa9e3e905L); /* 29 */
        d = GG(d, a, b, c, x[2], S22, 0xfcefa3f8L); /* 30 */
        c = GG(c, d, a, b, x[7], S23, 0x676f02d9L); /* 31 */
        b = GG(b, c, d, a, x[12], S24, 0x8d2a4c8aL); /* 32 */

        /* Round 3 */
        a = HH(a, b, c, d, x[5], S31, 0xfffa3942L); /* 33 */
        d = HH(d, a, b, c, x[8], S32, 0x8771f681L); /* 34 */
        c = HH(c, d, a, b, x[11], S33, 0x6d9d6122L); /* 35 */
        b = HH(b, c, d, a, x[14], S34, 0xfde5380cL); /* 36 */
        a = HH(a, b, c, d, x[1], S31, 0xa4beea44L); /* 37 */
        d = HH(d, a, b, c, x[4], S32, 0x4bdecfa9L); /* 38 */
        c = HH(c, d, a, b, x[7], S33, 0xf6bb4b60L); /* 39 */
        b = HH(b, c, d, a, x[10], S34, 0xbebfbc70L); /* 40 */
        a = HH(a, b, c, d, x[13], S31, 0x289b7ec6L); /* 41 */
        d = HH(d, a, b, c, x[0], S32, 0xeaa127faL); /* 42 */
        c = HH(c, d, a, b, x[3], S33, 0xd4ef3085L); /* 43 */
        b = HH(b, c, d, a, x[6], S34, 0x4881d05L); /* 44 */
        a = HH(a, b, c, d, x[9], S31, 0xd9d4d039L); /* 45 */
        d = HH(d, a, b, c, x[12], S32, 0xe6db99e5L); /* 46 */
        c = HH(c, d, a, b, x[15], S33, 0x1fa27cf8L); /* 47 */
        b = HH(b, c, d, a, x[2], S34, 0xc4ac5665L); /* 48 */

        /* Round 4 */
        a = II(a, b, c, d, x[0], S41, 0xf4292244L); /* 49 */
        d = II(d, a, b, c, x[7], S42, 0x432aff97L); /* 50 */
        c = II(c, d, a, b, x[14], S43, 0xab9423a7L); /* 51 */
        b = II(b, c, d, a, x[5], S44, 0xfc93a039L); /* 52 */
        a = II(a, b, c, d, x[12], S41, 0x655b59c3L); /* 53 */
        d = II(d, a, b, c, x[3], S42, 0x8f0ccc92L); /* 54 */
        c = II(c, d, a, b, x[10], S43, 0xffeff47dL); /* 55 */
        b = II(b, c, d, a, x[1], S44, 0x85845dd1L); /* 56 */
        a = II(a, b, c, d, x[8], S41, 0x6fa87e4fL); /* 57 */
        d = II(d, a, b, c, x[15], S42, 0xfe2ce6e0L); /* 58 */
        c = II(c, d, a, b, x[6], S43, 0xa3014314L); /* 59 */
        b = II(b, c, d, a, x[13], S44, 0x4e0811a1L); /* 60 */
        a = II(a, b, c, d, x[4], S41, 0xf7537e82L); /* 61 */
        d = II(d, a, b, c, x[11], S42, 0xbd3af235L); /* 62 */
        c = II(c, d, a, b, x[2], S43, 0x2ad7d2bbL); /* 63 */
        b = II(b, c, d, a, x[9], S44, 0xeb86d391L); /* 64 */

        state[0] += a;
        state[1] += b;
        state[2] += c;
        state[3] += d;
    }

    /*
     * md5Update是MD5的主计算过程，inbuf是要变换的字节串，inputlen是长度，这个 函数由getMD5ofStr调用，调用之前需要调用md5init，因此把它设计成private的
     */
    private void md5Update(byte[] inbuf, int inputLen) {

        int i;
        int index;
        int partLen;
        byte[] block = new byte[64];
        index = (int) (count[0] >>> 3) & 0x3F;

        // /* Update number of bits */
        if ((count[0] += (inputLen << 3)) < (inputLen << 3)) {

            count[1]++;
        }

        count[1] += (inputLen >>> 29);

        partLen = 64 - index;

        // Transform as many times as possible.
        if (inputLen >= partLen) {

            md5Memcpy(buffer, inbuf, index, 0, partLen);
            md5Transform(buffer);

            for (i = partLen; (i + 63) < inputLen; i += 64) {

                md5Memcpy(block, inbuf, 0, i, 64);
                md5Transform(block);
            }

            index = 0;
        } else {

            i = 0;
        }

        // /* Buffer remaining input */
        md5Memcpy(buffer, inbuf, index, i, inputLen - i);
    }
}